"""Aura API functions.
    Ref: https://neo4j.com/docs/aura/platform/api/specification/
"""
import requests
from requests.auth import HTTPBasicAuth

import config
from exceptions import ApiError
from exceptions import TokenExpired


def get_oauth_token() -> object:
    """To obtain a Bearer Token for authenticating API requests."""
    response = requests.post(
        f'{config.AURA_API_HOST}oauth/token',
        headers={'Content-Type': 'application/x-www-form-urlencoded'},
        data={'grant_type': 'client_credentials'},
        auth=HTTPBasicAuth(
            config.AURA_API_CLIENT_ID, config.AURA_API_CLIENT_SECRET)
    )
    data = response.json()
    assert data.get('access_token'), 'Error: No access_token'
    assert data.get('token_type', '') == 'Bearer'
    return data


def get_all_instances(token: object) -> list:
    """Returns a list containing a summary of each of your Aura instances.

    Returns: List of Instance objects.
    """
    response = requests.get(
        f'{config.AURA_API_BASE_URL}instances',
        headers={
            'Authorization': f"Bearer {token.get('access_token')}",
            'Content-Type': config.JSON_CONTENT_TYPE
        }
    )
    data = response.json()
    assert data.get('data'), "Error: No instances data"
    assert len(data.get('data', [])) > 0
    return data.get('data')


def get_instance_details(token: object, instance_id: str) -> object:
    """Returns details about a specific Aura Instance.

    Returns: Object.
    """
    response = requests.get(
        f'{config.AURA_API_BASE_URL}instances/{instance_id}',
        headers={
            'Authorization': f"Bearer {token.get('access_token')}",
            'Content-Type': config.JSON_CONTENT_TYPE
        }
    )
    data = response.json()
    if data.get('errors'):
        err_msg = ', '.join([item['message'] for item in data.get('errors')])
        raise ApiError(err_msg)
    elif data.get('error'):
        if 'token has expired' in str(data.get('error')):
            raise TokenExpired(str(data.get('error')))
        raise ApiError(str(data.get('error')))

    assert data.get('data'), f'Error: Instance with id {instance_id} not found.'
    assert data.get('data', {}).get('status'), \
        f'Error: Missing status for Instance {instance_id}.'
    return data.get('data')


def overwrite_instance(
        token: object, dest_instance_id: str, source_instance_id: str
) -> object:
    """Starts the process of overwriting the specified instance.

    A new snapshot of that instance is created and used for overwriting.
    Overwriting an instance is an asynchronous operation.

    Returns: Object.
    Throws: Exception. Eg:
        The database is currently undergoing an operation: overwriting.
        Cannot clone database b4820bcb into smaller database 8d6c00eb.
        The database is currently undergoing an operation: loading
    """
    response = requests.post(
        f'{config.AURA_API_BASE_URL}instances/{dest_instance_id}/overwrite',
        headers={
            'Authorization': f"Bearer {token.get('access_token')}",
            'Content-Type': config.JSON_CONTENT_TYPE
        },
        json={'source_instance_id': source_instance_id}
    )
    data = response.json()
    if data.get('errors'):
        err_msg = ', '.join([item['message'] for item in data.get('errors')])
        raise ApiError(err_msg)

    assert data.get('data'), \
        f'Error: Failed to overwrite Instance {dest_instance_id}.'
    assert data.get('data', {}).get('status'), \
        f'Error: Missing status for Instance {dest_instance_id}.'
    assert data.get('data').get('status') == 'overwriting', \
        (f"Error: Failed to start overwriting Instance {dest_instance_id}. "
         f"Status is still {data.get('data').get('status')}")

    return data.get('data')


def update_instance(
        token: object, dest_instance_id: str, cdc_mode: str
) -> object:
    """Update CDC enrichment mode on an Aura instance.

    Returns: Object.
    Throws: Exception. Eg:
        The database is currently undergoing an operation: overwriting.
        DB not found: 24d18db5
    """
    response = requests.patch(
        f'{config.AURA_API_BASE_URL}instances/{dest_instance_id}',
        headers={
            'Authorization': f"Bearer {token.get('access_token')}",
            'Content-Type': config.JSON_CONTENT_TYPE
        },
        json={'cdc_enrichment_mode': cdc_mode}
    )
    data = response.json()
    if data.get('errors'):
        err_msg = ', '.join([item['message'] for item in data.get('errors')])
        raise ApiError(err_msg)

    assert data.get('data'), \
        f'Error: Failed to update Instance {dest_instance_id}.'
    assert data.get('data', {}).get('status'), \
        f'Error: Missing status after updating the Instance {dest_instance_id}.'

    return data.get('data')